Re: [RFC] genalloc:add an gen_pool_alloc_align func to genalloc
From: Laura Abbott
Date: Mon Jul 13 2015 - 14:42:29 EST
On 07/12/2015 07:22 PM, Zhao Qiang wrote:
-----Original Message-----
From: Laura Abbott [mailto:labbott@xxxxxxxxxx]
Sent: Friday, July 10, 2015 5:51 AM
To: Zhao Qiang-B45475; lauraa@xxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx;
akpm@xxxxxxxxxxxxxxxxxxxx; olof@xxxxxxxxx; catalin.marinas@xxxxxxx; Wood
Scott-B07421; Xie Xiaobo-R63061
Subject: Re: [RFC] genalloc:add an gen_pool_alloc_align func to genalloc
On 07/09/2015 12:47 AM, Zhao Qiang wrote:
Bytes alignment is required to manage some special ram, so add
gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with align =
1 Byte.
Signed-off-by: Zhao Qiang <B45475@xxxxxxxxxxxxx>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc
directory, using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory, Scott wood
hopes to use genalloc to manage the muram, after discussing with
scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.
gen_pool supports custom allocation algorithms. I thought this was
discussed previously and the conclusion was that if you wanted alignment
you should use custom allocation algorithms. I'm failing at finding any
thread discussing it though.
Perhaps another option would be to add another runtime argument to
gen_pool where you could pass the alignment to your custom allocation
function. This way alignment isn't inherently coded into any of the
algorithms.
include/linux/genalloc.h | 10 +++++++---
lib/genalloc.c | 38 ++++++++++++++++++++++++++++++--------
2 files changed, 37 insertions(+), 11 deletions(-)
diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h index
1ccaab4..65fdf14 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -96,6 +96,8 @@ static inline int gen_pool_add(struct gen_pool *pool,
unsigned long addr,
}
extern void gen_pool_destroy(struct gen_pool *);
extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
+extern unsigned long gen_pool_alloc_align(struct gen_pool *, size_t,
+ unsigned long align);
extern void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size,
dma_addr_t *dma);
extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
@@ -108,14 +110,16 @@ extern void gen_pool_set_algo(struct gen_pool
*pool, genpool_algo_t algo,
void *data);
extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned
long size,
- unsigned long start, unsigned int nr, void *data);
+ unsigned long start, unsigned int nr, void *data,
+ unsigned long align_mask);
extern unsigned long gen_pool_first_fit_order_align(unsigned long
*map,
unsigned long size, unsigned long start, unsigned int nr,
- void *data);
+ void *data, unsigned long align_mask);
extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned
long size,
- unsigned long start, unsigned int nr, void *data);
+ unsigned long start, unsigned int nr, void *data,
+ unsigned long align_mask);
extern struct gen_pool *devm_gen_pool_create(struct device *dev,
int min_alloc_order, int nid);
diff --git a/lib/genalloc.c b/lib/genalloc.c index d214866..dd63448
100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -258,19 +258,22 @@ void gen_pool_destroy(struct gen_pool *pool)
EXPORT_SYMBOL(gen_pool_destroy);
/**
- * gen_pool_alloc - allocate special memory from the pool
+ * gen_pool_alloc_align - allocate special memory from the pool
* @pool: pool to allocate from
* @size: number of bytes to allocate from the pool
+ * @align: number of bytes to align
*
* Allocate the requested number of bytes from the specified pool.
* Uses the pool allocation function (with first-fit algorithm by
default).
* Can not be used in NMI handler on architectures without
* NMI-safe cmpxchg implementation.
*/
-unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+unsigned long gen_pool_alloc_align(struct gen_pool *pool, size_t size,
+ unsigned long align)
{
struct gen_pool_chunk *chunk;
unsigned long addr = 0;
+ unsigned long align_mask;
int order = pool->min_alloc_order;
int nbits, start_bit = 0, end_bit, remain;
@@ -281,6 +284,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,
size_t size)
if (size == 0)
return 0;
+ align_mask = ((align + (1UL << order) - 1) >> order) - 1;
nbits = (size + (1UL << order) - 1) >> order;
rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) { @@
-290,7 +294,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,
size_t size)
end_bit = chunk_size(chunk) >> order;
retry:
start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
- pool->data);
+ pool->data, align_mask);
if (start_bit >= end_bit)
continue;
remain = bitmap_set_ll(chunk->bits, start_bit, nbits); @@ -
309,6
+313,22 @@ retry:
rcu_read_unlock();
return addr;
}
+EXPORT_SYMBOL(gen_pool_alloc_align);
+
+/**
+ * gen_pool_alloc - allocate special memory from the pool
+ * @pool: pool to allocate from
+ * @size: number of bytes to allocate from the pool
+ *
+ * Allocate the requested number of bytes from the specified pool.
+ * Uses the pool allocation function (with first-fit algorithm by
default).
+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
+ */
+unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size) {
+ return gen_pool_alloc_align(pool, size, 1);
Passing 1 here would change the behavior of the existing algorithms which
were passing 0 for the align mask
When passing 1 here(align_mask = ((align + (1UL << order) - 1) >> order) - 1), align_mask will be 0.
It will not change the behavior of the existing algorithms.
Yes, you are right, I did the math wrong when looking at the align function.
Laura
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